Systemd
Tools
systemctl – Control the systemd system and service manager
list-timers [PATTERN...] | List timer units currently in memory, ordered by the time they elapse next. |
enable UNIT..., enable PATH... | Enable one or more units or unit instances. This will create a set of symlinks, as encoded in the “[Install]” sections of the indicated unit files. After the symlinks have been created, the system manager configuration is reloaded (in a way equivalent to daemon-reload), in order to ensure the changes are taken into account immediately. |
disable UNIT... | Disables one or more units. (won’t start automatically) |
mask UNIT... | Mask one or more units, as specified on the command line. This will link these unit files to /dev/null, making it impossible to start them. This is a stronger version of disable, since it prohibits all kinds of activation of the unit, including enablement and manual activation. Use this option with care. |
A unit file is a plain text ini-style file that encodes information about a service, a socket, a device, a mount point, an automount point, a swap file or partition, a start-up target, a watched file system path, a timer controlled and supervised by systemd(1), a resource management slice or a group of externally created processes. See systemd.syntax(7) for a general description of the syntax.
Usual tasks
systemctl status postfix
systemctl reload-or-restart postfixGet a list of enabled services
systemctl list-unit-files | grep enabledDisable a unit (service/timer) (won’t autostart, but it can still be run manually)
systemctl disable <service>Get systemd version
# systemctl --version
systemd 239List timers
systemctl list-timers --all
systemctl list-timers *apt*journalctl – Query the systemd journal
journalctl pipes its output to the less command, which shows your logs one page at a time in your terminal.
| -f, –follow | Show only the most recent journal entries, and continuously print new entries as they are appended to the journal. |
| -e, –pager-end | Immediately jump to the end of the journal inside the implied pager tool. |
| -r, –reverse | Reverse output so that the newest entries are displayed first. |
| -q, –quiet | Suppresses all informational messages (i.e. “– Journal begins at …”, “– Reboot –“), any warning messages regarding inaccessible system journals when run as a normal user. |
| -u,–unit=UNIT|PATTERN | Show messages for the specified systemd unit UNIT (such as a service unit), or for any of the units matched by PATTERN. This parameter can be specified multiple times. |
| –user-unit= | Show messages for the specified user session unit. |
| -S, –since=, -U, –until= | Start showing entries on or newer than the specified date, or on or older than the specified date, respectively. |
| –disk-usage | Shows the current disk usage of all journal files. This shows the sum of the disk usage of all archived and active journal files. |
| –rotate | Asks the journal daemon to rotate journal files. |
| –vacuum-size=, –vacuum-time=, –vacuum-files= | Removes the oldest archived journal files until the disk space they use falls below the specified size/older than/specified number of separate journal files |
| -x, –catalog | Augment log lines with explanation texts from the message catalog. This will add explanatory help texts to log messages in the output where this is available. |
Show journal and follow
journalctl -fShow journal and follow, showing only a certain unit
journalctl -f -u NetworkManager
journalctl -f -u pvedaemonShow today’s logs associated to a certain unit
journalctl -S today -u sanoid.service
journalctl -f -S today -u sanoid.service -u syncoid.serviceImmediately jump to the end of the journal inside the implied pager tool
journalctl -e Get the log at a specific time
journalctl --since "2020-08-22 23:15:00" --until "2020-08-22 23:45:00"List boots
journalctl --list-bootsShow all messages from this boot (and last boot)
journalctl -b
journalctl -b -1From: https://wiki.archlinux.org/index.php/Systemd/Journal
https://www.freedesktop.org/software/systemd/man/journalctl.html
Clear logs
https://linuxhandbook.com/clear-systemd-journal-logs/
networkctl – Query the status of network links
networkctl list
networkctl status -a
timedatectl – Control the system time and date
timedatectl may be used to query and change the system clock and its settings.
$ timedatectl
Local time: Tue 2021-10-12 12:06:50 CEST
Universal time: Tue 2021-10-12 10:06:50 UTC
RTC time: Tue 2021-10-12 10:06:50
Time zone: Europe/Berlin (CEST, +0200)
System clock synchronized: yes
NTP service: active
RTC in local TZ: notimedatectl list-timezonestimedatectl set-timezone Europe/Berlin$ timedatectl status
$ timedatectl timesync-status
$ timedatectl show-timesync --all$ vi /etc/systemd/timesyncd.conf
$ systemctl restart systemd-timesyncd.serviceinfos: https://wiki.archlinux.org/title/systemd-timesyncd
systemd-resolve
systemd-resolve – Resolve domain names, IPV4 and IPv6 addresses, DNS resource records, and services
systemd-resolve --status
systemd-resolve debian.org
systemd-resolve 130.89.148.77
systemd-resolve 2603:400a:ffff:bb8::801f:3ehttps://wiki.archlinux.org/index.php/Systemd-resolved
systemd-resolve --flush-caches
systemd-resolve --statisticssystemd-analyze – Analyze and debug system manager
As bootchart as been merged in systemd, it is possible to plot the boot sequence to discover what is taking time.
systemd-analyze plot > systemd-analyze-ares.svgsystemd/Timers
systemctl list-timerssystemctl status sanoid.timer
sudo systemctl enable sanoid.timer
sudo systemctl start sanoid.timerhttps://wiki.archlinux.org/title/Systemd/Timers
Random
Important folders
/etc/systemd/Units
man systemd.unit